1. Field of the Invention
The present invention relates generally to radio systems and, more specifically, to synchronizing or scheduling communications sessions between two radio transceivers.
2. Description of the Related Art Maximizing battery life in portable two-way radios (transceivers) is highly desirable. Transceivers that are known in the United States as Family Radios have a battery life of about 30 hours for alkaline and about eight hours for nickel-cadmium rechargeable batteries. The economical Family Radios are increasingly popular with outdoor enthusiasts and those traveling in groups who wish to stay in contact with one another over short distances. These radios are essentially FM-band versions of the venerable device commonly known as a xe2x80x9cwalkie-talkiexe2x80x9d or Citizens"" Band radio. Family radios are used in essentially the same manner as a walkie-talkie, though some have additional features. For example, some Family Radios have a paging feature by which a first user can transmit an alert signal to a second user that indicates the first user wishes to initiate a conversation.
Various power-conservation circuits and methods and known in the art, but they are believed to be unduly complex and accordingly uneconomical. Therefore, such circuits and methods are not well-suited for Family Radios, because low cost is one of their most notable attributes and has contributed to their widespread acceptance by the public. It would be desirable to provide an economical power-conservation method and system that would be well-suited to not only Family Radios but also other types of two-way radios and cellular telephones. The present invention addresses this problem and others in the manner described below.
The present invention relates to a method and system for synchronizing communications sessions between two or more radio transceivers. In accordance with the method, a duty cycle is first established. The duty cycle may be established by having the users who intend to communicate with each other mutually agree upon a duty cycle. The duty cycle is defined by an on-time and an off-time. The on-time is determinative of the time at which a communication session is to be enabled by switching the transceiver from a power-conserving sleep state to a powered-on or active state. The off-time is determinative of the time at which a communication session is to be disabled by switching the transceiver from the active state back to the sleep state. The on-time and off-time may, in some embodiments of the invention, be established relative to the current time-of-day rather than in absolute terms or relative to some other parameter.
In an exemplary embodiment of the invention, the duty cycle information is communicated from one transceiver to the other(s). In an embodiment of the invention in which the on-time and off-time that are communicated are established relative to the time of day, the then-current time of day may be communicated as part of the duty cycle information along with the on-time and off-time. In the exemplary embodiment, the duty cycle information includes the then-current time of day, the start time (i.e., the time of day at which the active state is to be entered), the active length (i.e., the time during which the transceiver is to remain in the active state), and the sleep length (i.e., the time during which the transceiver is to remain in the sleep state).
In the exemplary embodiment, a microprocessor monitors the on-time. When the on-time indicates that the transceiver is to be powered-on from the sleep state to the active state, the microprocessor causes power to be applied to the power distribution grid. This applies power to the various other circuitry of the transceiver, including the radio frequency transmitter and receiver circuitry. Because they are synchronized, all transceivers of the system simultaneously power-on in this manner. In the active state, there is sufficient power for radio communication between the transceivers, and the users can use the transceivers in the conventional manner during the active state. The transceivers remain in the active state until the off-time indicates to the microprocessor that the transceiver is to be powered-off from the active state to the sleep state. The cycle repeats periodically in accordance with the duty cycle information.
The above-described system and method allows two or more users to, in effect, check in with each other at agreed-upon times such as every half hour. But rather than having them continually check their (most likely poorly synchronized) wristwatches and attempt to turn on their radios at the agreed-upon times, the invention automatically synchronizes the radios and turns them on at the agreed-upon times, thereby eliminating the potential for human error and freeing the users"" attention for other tasks. Although any selected duty cycle is suitable, even a very short duty cycle can be effective at reducing power consumption. For example, having the radios turn on every other minute would double battery life over a conventional radio system.
The foregoing, together with other features and advantages of the present invention, will become more apparent when referring to the following specification, claims, and accompanying drawings.
For a more complete understanding of the present invention, reference is now made to the following detailed description of the embodiments illustrated in the accompanying drawings, wherein:
FIG. 1 is a time-line illustration of two radio transceivers of the present invention;
FIG. 2 is a flow diagram of a synchronization method;
FIG. 3 is a block diagram of a transceiver having a synchronization system;
FIG. 4 illustrates a transmission record;
FIG. 5 illustrates synchronization control data stored in the transceiver memory;
FIG. 6A is part of a flow diagram illustrating a method of the present invention;
FIG. 6B is a continuation of the flow diagram of FIG. 6A;
FIG. 6C is a continuation of the flow diagram of FIGS. A-B;
FIG. 6D is a continuation of the flow diagram of FIGS. A-C;
FIG. 6E is a continuation of the flow diagram of FIGS. A-D;
FIG. 6F is a continuation of the flow diagram of FIGS. A-E;
FIG. 6G is a continuation of the flow diagram of FIGS. A-F; and
FIG. 6H is a continuation of the flow diagram of FIGS. A-G.